Some very good insight in this thread. I have nothing startling to add, but I do have a success story to share, in case you do decide to continue with this horse.
I had a mare who was extremely barn sour. She was very hot, half Arabian, and the method of bringing her home and working her would’ve had zero effect. She had no bottom.
What worked for me was to turn home and give her a completely long rein. I mean On The Buckle.
Of course she would try to take off…and I would do an ignorant version of the John Lyons exercise above.
I have never heard of that exercise, but I did a tiny tiny circle and we did not progress from that circle until she walked.
The second she walked I gave her a long rein towards home, and she would takeoff and we would do it again.
We had about four come to Jesus rides.
It took us about an hour and a half to get home from one mile out.
Fortunately, in addition to being hot as snot, she was also very smart. She did figure out that walking was the only gait that was going to get her going in the direction she wanted.
We arrived at a functional agreement that she could have a long rein and walk as quickly as she wanted.
It had to be black-and-white.
I was not successful the transitioning into walking on contact Home, but I decided that really didn’t matter.
The only downside was that she had an extraordinarily huge walk for a horse her size, and no other horses except one could really keep up with her. She also didn’t care if she left other horses in the dust on that walk home. So, I did consider this a success… And it did last as long as I had her.